Electrophysiology of the pulmonary vein in the left atrial volume-load model

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Electrophysiology of the pulmonary veins in a left atrial volume-load model was studied. A shunt was made between the left subclavian artery and the left pulmonary artery in mongrel dogs. All the animals exhibited severe heart failure postoperatively. Some animals died of severe heart failure. The animals survived for 4 weeks were subjected to the pulmonary vein mapping study. Conduction velocity of the pulmonary veins was measured during pacing by means of custom-made a multi-electrode catheter. Data were compared with those obtained from the normal control animals. Diameter of each pulmonary vein was measured and myocardium sleeve extending into the pulmonary veins was examined microscopically.The conduction velocity decreased in the circumferential direction of the pulmonary veins in the volume-loaded animals. The change of the conduction velocity in the longitudinal direction varied and there was no significant difference between the control animals. Histological examination revealed that the myocardial sleeve was stretched and thinned in the circumferential direction. Fibrosis was also present. It remains uncertain whether the decrease in the conduction velocity was due to true decrease in the conduction velocity or increase of the caliber of the pulmonary vein.